GCN Circular 22563
Subject
Swift Trigger 819863 is not a GRB
Date
2018-03-30T03:23:32Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Deich (PSU), H. A. Krimm (NSF/USRA), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:
At 03:09:02 UT, the Swift Burst Alert Telescope (BAT) triggered during
the count rate increase during the approach to the SAA, and found
a low-significance peak in the resulting image (trigger=819863).
Swift slewed immediately to the location.
The BAT on-board calculated location is
RA, Dec 95.803, -64.954 which is
RA(J2000) = 06h 23m 13s
Dec(J2000) = -64d 57' 12"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a continuous
increase as expected on entering the SAA.
The XRT began observing the field at 03:10:27.2 UT, 85.1 seconds after
the BAT trigger. However, the source automatically identified on-board
was a cosmic ray, caused by the proximity of Swift to the SAA.
Due to the low significance of the image (6.55 sigma), the lack
of a GRB-like peak during the increasing particle background, and
the non-detection of an afterglow by XRT, we believe that
this is not a GRB.